1. Field of the Invention
The present invention relates to trench cutting and pipe burying devices for use in an undersea marine environment. The present invention more particularly provides a pipe burying jet sled with an improved spoil removal means which scoops and transmits spoil material cut to the air lift spoil intake portions of the jet sled for subsequent removal from the trench.
2. General Background and Prior Art
Many devices have been patented and have been used commercially for excavating an underwater ditch or trench, with a pipeline which has been welded together and constructed laid in the ditch for subsequent protective coverage a distance beneath the sea bed. Underwater trench cutting devices attempt to solve the problems of properly cutting a ditch of desired depth and shape, of loosening the sea bed material into a spoil which could be removed, and removing the spoil material from the area around the trench so that it does not refill the trench after the jet sled or like device has passed and before pipe is placed in the trench or ditch.
In U.S. Pat. No. 3,504,504 also issued to H. A. Elliot, a similar type eductor tube is utilized to discharge soil cuttings or spoil. The eductor tubes are mounted on a pair of concave jaw scoop members with the jaw scoops channelling cuttings mud and slurry to the eductor tubes. Openings fore and aft allow the pipeline to pass through the pair of jaw scoops which are movably mounted with respect to one another to vary the distance therebetween, allowing the pipe to be placed between the scoop jaws during operation.
U.S. Pat. No. 3,368,358 issued to H. A. Elliot provides a trenching machine which utilizes a pair of scoop jaws similar to those in U.S. Pat. No. 3,504,504 and eductor tube for discharging soil or formation materials cut by the jetting action of the sled.
In U.S. Pat. No. 3,751,927 two vertically oriented eductor pipes discharge spoil and cuttings with the aid of a high pressure fluid conduit. The pressurized fluid is injected into the eductor head tubes to enhance spoil removal.
U.S. Pat. No. 4,041,717 provides a sand shield jet sled which prevents unconsolidated materials such as sand, from entering the sea bed prior to the placement of the pipe to be buried into the trench. Elongated members extending rearwardly of the jet sled and having shields depending therefrom physically restrain the walls of the trench from caving in and filling the trench beneath the unsupported portion of the pipe.
These and other prior art devices suffer in that they fail to provide an adequate means for channelling or transmitting material which has been cut, i.e. spoil, in the area of the discharge of a provided eductor tube or air lift conduit.
Generally, if a channelling means or scoop is provided to move soil cuttings and the like to the air lifts for removal, it is complex, requiring automated winches and cables for its opening and closing when placing or removing the jet sled on a pipeline to be buried.
Since soil cut will usually settle somewhat a scoop should have air lifts at the bottom of the scoop, or soil cuttings will accumulate in that area not occupied by the air lift, effectively clogging the scoop and limiting its effective size and efficiency.
On some prior art type scoops used with jetting legs, the pipeline passes during operation through the scoop, requiring both fore and aft openings in the scoop, which allows the escape of soil cuttings through the aft opening as the sled progresses.
Therefore, it is an object of the present invention to provide a jet sled apparatus which is provided with a simple to operate, efficient spoil collection scoop surrounding the spoil intake portion of the jet sled air lift for consolidating soil cuttings and enhancing their removal from the trench area.
It is another object of the present invention to provide a spoil scoop structure with air lift intakes provided at a lowermost portion of the scoop thereby removing all soil cuttings from the scoop and also removing the chance for soil cutting accumulation in the scoop.
It is another object of the present invention to provide a jet sled and spoil collection scoop having only a forward opening and no opening aft during operation from which spoil collected can escape.
It is another object of the present invention to provide a jet sled and spoil collection scoop apparatus with air lift intake at variable level.
Still another object of the present invention is to provide a jet sled and spoil collection scoop apparatus with the scoop being easily manually opened and closed by a diver allowing easy mounting or dismounting of the apparatus on a pipeline to be buried.
It is another object of the present invention to provide a jet sled for burying pipe in a sea bed which is simple and easy to manufacture.
3. General Description of the Present Invention
The present invention solves all the prior art problems and shortcomings by providing a pipe burying apparatus having a frame with a central pipeline passage allowing a pipeline to be buried to pass therethrough during the burying operation. The frame is adapted for undersea towing and has left and right jetting means mounted on the frame on the left and right sides respectively of the central pipeline passageway, the jetting means cutting a trench in the sea bed with the subsequent placement of a pipeline to be buried therein. Left and right air lift conduits each provides spoil intake and spoil discharge portions for removing soil cuttings from the trench as they are cut by the jetting means, the spoil intake portions being placed generally behind and between the left and right jetting means. A spoil collection scoop is mounted on the frame generally below the central pipeline passageway portion of the frame and surrounding the bottom, sides, and rear portions of the soil intake portions of the air lifts. The spoil collection scoop provides bottom and rear door portions, each of which is movably mounted on the frame between open and closed positions, and each of which can be removed from the frame if desired. The spoil intake portions of the air lifts are mounted in the scoop at the bottom and rear portions thereof solving the problem.